I realize it's probably too late..but the power lines just before the Mass Pike down on Rt 49. From Spencer travel south until you go over the Mass Pike, now turn around and head back towards Spencer as you cross over the MP now look on your right for the power lines and trail...it's also across from the State Park...can't remember the name.
Power lines are not legal wheeling in MA. Good way to get more legal places shut down. If you want to wheel, join a club and keep the few trails that are still legal open. Or find out which ones actually are legal and stick with those!